Select vertices on one side of a cube
You could use some vector math to select the right facing verts (deselect all verts and run this in object mode in the text editor, or paste in the console)

from bpy import context as C
from mathutils import Vector

for v in (v for v in C.object.data.vertices if v.normal.dot(Vector((1,0,0))) &gt; 0):
    v.select = True


alternately, to select the left side, change the Vector to (-1,0,0). Top, (0,0,1) etc.